WPB-25328 autopromotion for adminless groups

[battermann]

https://wearezeta.atlassian.net/browse/WPB-25328

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines

[Copilot]

Pull request overview

Implements “Prevent adminless groups” autopromotion behavior so that when a team conversation would become adminless (e.g., last admin leaves or is removed via team-member deletion), eligible members can be promoted automatically depending on the configured promotion strategy.

Changes:

• Adds a pure selection helper (selectAutopromotionCandidate) and unit tests for strategy-based autopromotion candidate selection.
• Extends the conversation removal flow (removeMemberQualified / guardPreventAdminlessGroups) to trigger autopromotion for legacy responses, and introduces a ConversationSubsystem operation to clean a user out of all team conversations while applying the guard.
• Updates Galley API call sites and integration tests to cover autopromotion on v15 leave and on team member deletion / user deletion.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
services/galley/src/Galley/API/Teams.hs	Routes team-member deletion cleanup through ConversationSubsystem (deleteUserFromTeamConversations).
services/galley/src/Galley/API/Public/Conversation.hs	Adapts remove-member endpoints to updated removeMemberQualified conn-id shape (Maybe ConnId).
services/galley/src/Galley/API/LegalHold.hs	Switches policy-conflict removals to use removeMemberQualified.
libs/wire-subsystems/wire-subsystems.cabal	Registers new AdminlessGroups module and its unit spec in cabal.
libs/wire-subsystems/test/unit/Wire/ConversationSubsystem/InterpreterSpec.hs	Extends interpreter spec error stack for new error paths involved in removal/autopromotion.
libs/wire-subsystems/test/unit/Wire/ConversationSubsystem/AdminlessGroupsSpec.hs	Adds unit coverage for autopromotion strategy selection behavior.
libs/wire-subsystems/src/Wire/ConversationSubsystem/Update.hs	Implements autopromotion guard behavior and team-conversation cleanup implementation.
libs/wire-subsystems/src/Wire/ConversationSubsystem/Interpreter.hs	Wires new ConversationSubsystem operation into the interpreter.
libs/wire-subsystems/src/Wire/ConversationSubsystem/AdminlessGroups.hs	New pure helper module for deterministic autopromotion candidate selection.
libs/wire-subsystems/src/Wire/ConversationSubsystem.hs	Adjusts subsystem API (conn-id optionality; new DeleteUserFromTeamConversations operation).
integration/test/Test/AdminlessGroups.hs	Adds integration coverage for autopromotion on v15 leave and deletion scenarios.
changelog.d/2-features/WPB-25313	Updates changelog entry text for the feature (but ticket/file mismatch vs PR).

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